Saint Louis (25-3, 12-1 Atlantic 10) had not lost since dropping a 70-65 decision Dec. 1 to unbeaten Wichita State, now ranked No. 2 in the country.

Mason, who entered leading the nation in 3-point shooting percentage (.554), hit 4-of-5 from behind the arc for Duquesne (12-15, 4-10), which beat a top-10 opponent on the road for the fifth time (5-28). The Dukes, who were 14-point underdogs, improved to 25-55 against teams ranked in the top 10.

Dwayne Evans had 10 points and 12 rebounds for Saint Louis. Mike McCall Jr. led the Billikens with 18 points, while Jordair Jett (13 points) and Rob Loe (12 points) also were in double digits.

Saint Louis, which could have clinched at least a tie for the Atlantic 10 regular-season title, will try to rebound Saturday when it visits VCU.

The Dukes played Saint Louis tough in their first meeting, losing 76-72 at home Jan. 22. Duquesne was up for the challenge again Thursday and showed it early as Mason hit his first two from behind the arc to help the Dukes grab a 13-8 advantage.